This invention relates in general to electrical outlets, such as receptacles and switches, which are particularly advantageous for use in buildings of light-frame construction wherein the building framing is surfaced on two sides to form two substantially planar surfaces which are parallel to each other, and which enclose the framing structure. In the last 20 years, wages in virtually all construction trades have rapidly increased, and with these rapid increases in labor costs, ways must be found to reduce labor requirements in construction methods if inflation in building costs is to be controlled. One area where considerable labor reduction appears possible is in the installation of electrical distribution systems. Despite advances in wall construction methods, electrical outlets are still installed in much the same way as when electrical lines were first concealed in plaster walls at the turn of the century.
The earliest electrical systems were surface mounted, but it soon became common practice to install wiring in the voids between framing members to be concealed by the surface materials, with switches and receptacles still surface mounted. Soon public desires sought to finish these elements essentially flush with the surface to minimize visibility of the electrical distribution system. Plaster remained the most common wall and ceiling material for many years. As a wet process, plastering required the placement of a junction box to define a space within which the switch or receptacle element could be placed upon completion of the plastic surface. The junction box also accomodated the various circuit cables terminating at each switch or receptacle location, and excess wiring left to facilitate connections could be folded up in the back of the junction box behind the outlet element and cover plate. Because electrical outlets had to be fastened to a structural member, and because plaster could not easily be cut for the junction box after setting, junction boxes were installed prior to plastering. Electrical codes designed to protect the public soon came to require that all electrical connections (including those made to outlet elements) be made in approved junction boxes.
Electrical distribution systems were typically installed in buildings having plastered wall and ceiling systems over wood-frame construction in the following sequence: first, open-front metal junction boxes were fastened to wall studs or ceiling joists depending upon the desired function of the outlet (i.e. whether it was to be a receptacle, switch, lighting fixture, etc). Circuit wiring was then run between the framing members from the circuit panel to junction boxes and between such junction boxes. Wires were inserted in the junction boxes and clamped to the back or side thereof. Then, lath and plaster were placed around the opening defined by the front of the junction box, and the ends of the wires were stripped, connected to terminal screws on the receptacle or switch element, which was then fastened into the junction box. Finally, after the wall surfaces were painted, either a cover plate or fixture was installed to cover the exterior of the junction box.
During the 1950's, plaster surface techniques were virtually eliminated from wood-frame construction with the widespread acceptance of gypsum wallboard panels which provide a smooth, planar interior wall surface similar to plaster, but with much less effort and at lower cost. However, the success of gypsum board did nothing to alter the installation sequence (which originated with wet plaster wall surfacing techniques) for the electrical distribution network, requiring a number of distinct operations by an electrician.
While junction boxes have traditionally been made of pressed or formed sheet metal, fiber glass reinforced junction boxes are now finding similar applications. Switch and receptacle elements installed in such junction boxes normally have a hard, insulating plastic body surrounding metal conductors, with exposed screws at their sides to which the wire leads are connected. However, recently switch and receptacle elements have appeared which replace the aforementioned more common screw-type terminals with plug-in-type devices which utilize a spring-type gripper to insure electrical contact. Some of the types of devices just discussed above herein are disclosed, for example, in Dorfman U.S. Pat. No. 2,428,110, Palmer U.S. Pat. No. 3,119,895, Schindler et al U.S. Pat. No. 3,701,451, Osinski U.S. Pat. No. 2,397,688, and Smith U.S. Pat. No. 3,488,428.
Electrical outlet installation presently has unusually high labor content by comparison with other construction operations. This situation results both from the need for three or four trips by the electrician to each outlet location, as well as from the large amount of time required to connect and install the parts themselves at each such location. In addition to their high labor content, present electrical outlet systems have several other drawbacks. The finished appearance is often unsatisfactory due to installation of the receptacle or switch element at a slight angle (which determines the angle of the cover plate), or due to improper depth setting of the junction box such that the cover plate, the last item installed, does not fit flush against the wall surface. More importantly, present systems may present unnecessary safety hazards. Cover plates are rather simply attached and may easily be removed by children to expose bare conductors and terminal screws. Also, most present installations have considerable bare metal exposed behind the wall, including metal boxes, clamps, and fasteners which, in the event of a short circuit, could be a source of severe electrical shock to anyone coming into accidental contact with such exposed parts. Finally, present systems can cause great difficulty to repairmen in the event of a faulty wire between junction boxes. The wire cannot readily be removed and replaced without removing the junction box, yet the junction box cannot be removed without removing a portion of the wall. If the junction box could more easily be removed, the faulty wire could also be more easily replaced, including using it to pull a replacement wire through the same path, without requiring the removal of a portion of the wall around the junction box.